Technical Field
The present invention relates to a power conversion apparatus.
Background Art
A power conversion apparatus that converts input AC (Alternating Current) power into DC (Direct Current) power and that outputs the DC power includes a gate driver unit and a power module.
The gate driver unit (GDU) includes a gate substrate. The gate substrate has mounted thereon a gate driver circuit component for isolating a control signal input from a control apparatus outside the power conversion apparatus, for converting the isolated control signal into a gate signal, and for outputting the gate signal.
The power module includes, for example, a switching element and a freewheeling diode connected in inverse-parallel to the switching element. The switching element is turned on or off in accordance with a gate signal input from the gate driver unit via a gate control line. The freewheeling diode causes a current generated upon turning on the switching element to detour around the switching element so as to prevent a failure of the switching element.
The gate driver circuit component includes a gate resistor. The gate resistor is connected to a gate control line between the gate driver unit and the switching element. The gate resistor suppresses a surge voltage generated upon turning off the switching element or noise generated upon switching so as to stabilize a gate signal input to the switching element.
Recently, wide bandgap semiconductors have been sometimes used for switching elements in power modules. An exemplary wide bandgap semiconductor is a SiC (silicon carbide)-MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). In comparison with a Si (Silicon)-based switching element such as a Si-IGBT (Insulated Gate Bipolar Transistor), a wide bandgap semiconductor may have pressure resistance and achieve fast switching. To enable fast switching of a switching element comprising such a wide bandgap semiconductor, a gate resistor needs to be operated effectively. Hence, the gate electrode is desirably located near the switching element.
A gate driver unit described in Japanese Laid-open Patent Publication No. 2015-198545 includes a first substrate (gate substrate) and a second substrate (gate relay substrate) that is fixed to a gate terminal of a power module by soldering or the like. A gate resistor is mounted on the second substrate. The second substrate is connected to the first substrate by a gate control line. The gate control line is fixed to the first and second substrates by soldering or the like. A well-known example of the gate control line is a wiring conductor plate wherein a gate wire and a source wire (ground wire) form a laminated structure with an insulation sheet interposed therebetween so as to decrease the wiring inductance of a gate circuit.
The gate driver circuit component and the power module may be expensive. Hence, when one of the gate driver circuit component or the power module has failed, it is desirable to replace only the faulty one. However, when the gate substrate having the gate driver circuit component mounted thereon and the gate relay substrate fixed to the power module have been fixed to the gate control line, the gate driver circuit component and the power module cannot be readily separated from each other. Thus, even when only one of the gate driver circuit component or the power module has failed, not only the faulty one but also the other one, i.e., the normal one, needs to be replaced, thereby leading to a high repair cost.